Eric Kulcyk wrote:

> I have a scene with a ground plane and a cone hanging in mid-air, which is a
> perfect mirror.  My camera is pointed up at the mirror.  I would like to
> determine, for a given pixel on the ground plane, which pixel (if any) it
> corresponds to in the image, forming a lookup table.  Is there any way to do
> this?

if the setup is such that you can restrict yourself to a finite
rectangle in the plane, choose that rectangle and apply two color
gradients to it, such that red goes from 0 to 1 in x direction,
and blue goes from 0 to 1 in z direction (so your corners are
black, red, blue, magenta).

In the rendered image, the red and blue channels will contain the
originating coordinates after appropriate scaling. you need to use
a 16 bit output format to represnt more than 256 coordinate steps.

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